Current high performance and high altitude aircraft, such as those currently used by the United States military, are capable of flight maneuvers that exceed the limits of the unprotected human body. In the event the acceleration rate exceeds the limit of the human body, the crew member becomes unconscious for a brief period of time because the blood leaves the brain and pools in the abdomen and lower extremities. The aircraft may also fly at altitudes above the safe limit for the human body.
Blacking out due to a high acceleration level is termed "G-induced loss of consciousness" (G-LOC). If G-LOC occurs at low altitudes or when the aircraft nose is pointing downward, the pilot may not regain consciousness prior to ground impact. To reduce the occurrence of G-LOC, crew members of current aircraft wear anti-G suits which apply pressure to the abdomen and lower extremities to restrict blood from pooling there and to reduce the loss of blood from the brain. Crew members also perform an M-1/L-1 straining maneuver to prevent the blood pressure in the brain from decreasing Recent aircraft have also included positive pressure breathing devices and chest counterpressure systems to further increase the crew's tolerances for G-forces and high altitude flight. At high altitudes, a full garment, the partial pressure suit, has been demonstrated to protect the human body from hypoxia, and eventual unconsciousness during flight.
The anti-G system, which includes the anti-G garments, positive pressure breathing and chest counterpressure devices and partial pressure suit are coupled to a source of fluid under pressure via a connector. When the pilot ejects from the aircraft, he carries with him the anti-G garment, which must be separated from the source of pressurized gas provided by the aircraft. In current aircraft, the connector which couples the anti-G system to the source of fluid under pressure provides pull-apart, quick-disconnect coupling to permit the pilot to cleanly and quickly eject from the aircraft.
The pull-apart connection between the anti-G suit and the source of pressurized fluid has been demonstrated to allow inadvertent and undetected disconnection during flight because of normal in-cockpit motion of the air crew. When the anti-G suit becomes disconnected from the source of pressurized fluid while in flight, the anti-G suit will not provide the required protection against unconsciousness. The crew member, unaware of the nonoperational state of his anti-G suit, may perform a high acceleration maneuver, causing G-LOC, or fly at high altitudes, causing hypoxia, and resulting in a possible fatality. Improvements in the pull-apart connector have resulted in new connectors that resist inadvertent separation; however, the resulting increase in complexity, bulk and weight makes them extremely difficult for use in a high performance aircraft. Further, some of the improved pull-apart or quick-disconnect designs which should separate only when the pilot is leaving the aircraft, either by ejection or after landing, have been demonstrated to fail and leave the pilot unprotected.
Systems for testing the operation of the anti-G suit at the factory and while on the ground just prior to each flight have been introduced to minimize the chance that the pilot will be left unprotected while in flight; see, for example, U.S. Pat. No. 4,336,590, to Jacq et al., incorporated herein by reference. Such test systems simulate various flight conditions, including accelerations and high altitudes, to test whether the entire system is working properly.
If the system does not work properly, an alarm is triggered. A significant disadvantage of the current systems is that they are not designed for operation while in flight. Prior to flight, the pressurization of the anti-G garment can follow a preselected test pattern because the aircraft has not yet left the ground. However, once the aircraft is airborne, a variety of different flight conditions will change the environment causing the pressure provided to the anti-G suit to vary constantly, the crew members may move, or the system may be damaged such as by a hit from an enemy, making use of a preset test pattern unreliable for suit status at a later time while in flight. Another disadvantage of current systems is that they use the same flight condition sensors and system for the test as is used during the flight. While using the same sensors and systems for test and actual in-flight anti-G suit protection provides the advantage of testing the components, it has the disadvantage that it temporarily disables the entire system and leaves the crew member unprotected during a test.